This invention relates to a speed changing device for a bicycle, and more particularly to a speed changing device capable of controlling a front and a rear derailleur by one control lever.
This kind of speed changing device has hitherto been proposed. U.S. Pat. No. 3,808,907 discloses a speed changing device in its specification and drawings, which is so constructed that a drum is rotatably supported to a base member, one control lever is rotatably supported to a shaft extending from the drum perpendicularly with respect to the axis thereof, a control wire for a rear derailleur is attached at one end to the lever, a link mechanism is provided in association with the drum, and a control wire for a front derailleur is attached at one end to the link mechanism, so that the lever is turned with respect to the drum to control the rear derailleur and the lever is turned to rotate the drum to thereby control the front derailleur. This construction is not only complicated but also the lever must be turned in different directions to control the rear and front derailleurs, resulting in a complex operation and the occurrence of malfunctions.
Furthermore, the control mechanisms for the front and rear derailleurs are not separated but are interconnected and used exclusively to control both the front and rear derailleurs. Hence, this prior art device cannot be separated and used for controlling only one derailleur, e.g., the rear derailleur.
In order to overcome the above problem, this invention has been designed. An object of the invention is to provide a speed changing device which is simple in construction and capable of selectively controlling the front or rear derailleur simply and reliably, while being easily separated to form a speed changing device for the front or rear derailleur only, thus being widely usable.
In detail, the speed changing device of the invention is provided with one lever unit comprising a control lever, a first winding body carrying a first control wire connected to one of the front and rear derailleurs, and engaging means for selectively transmitting rotation of the lever to the first winding body, and with a winding unit including a second winding body which has an engaging portion engageable with the engaging means and carries a second control wire connected to the other derailleur, the winding unit being detachably mounted to the lever unit through coupling means.
The lever unit coupled with the winding unit enables one control lever to readily control both the front and rear derailleurs. On the other hand, the lever unit, when the winding unit is removed therefrom, is readily changeable to a speed control device for a front or rear derailleur only. Hence, the speed changing device of the invention is adapted to be configured to meet a user's requirements. Namely, the user, when using the rear derailleur only, need only buy the lever unit, because each of the lever unit and winding unit is individually salable as a bicycle part, thereby saving his expense to the extent the winding unit is not needed. Furthermore, since the lever unit is adapted to control two derailleurs by use of the single control lever, the user, who has equipped his bicycle with the lever unit together with the rear derailleur, can merely couple the winding unit with the lever unit simply and inexpensively when he wants to add the front derailleur.
These and other objects and novel features of the invention will be more apparent from the following description in accordance with the accompanying drawings.